Getting a grip

Wrinkled wet fingers belong in the bigger evolutionary picture, scientists reveal.

New Statesman
A baby's wrinkled finger after getting out of the bath (Wiki Commons, Fir0002/Flagstaffotos)

The prune-like fingers we get after swimming, washing-up without gloves or stewing in the bath, for perhaps a little too long, are common to us all.

Scientists have now discovered that wrinkled skin serves a purpose: they help humans grip wet objects or objects under water.

In an experiment reported in the Royal Society’s journal, Biology Letters, Newcastle University scientists studied people taking objects out of water with wrinkled fingers and again with dry fingers to explain why the effect occurs.

Author and neurobiologist, Dr Tom Smulders said: “We have showed wrinkled fingers give a better grip in wet conditions – it could be like treads on your car tyres which allow more of the tyre to be in contact with the road and gives you a better grip.”

Twenty participants transferred 45 marbles submerged in water from one container to another with both dry and wet hands.

The task took between 90 and 150 seconds to complete but, on average, those with wrinkled fingers moved the objects in 12 per cent less time (15 seconds faster) than those who began with dry hands.

Wrinkled fingers made no difference for moving dry objects, however.

The senior lecturer added:

Going back in time this wrinkling of our fingers in wet conditions would have helped with gathering food from wet vegetation or streams. And as we see the effect in our toes too, this may have been an advantage as it may have meant our ancestors were able to get a better footing in the rain.

Formerly, it was believed that our digits shriveled as the result of skin swelling in water, but recent research has shown that this is caused by blood vessels constricting in reaction to the water and forcing the skin to fold.

That this response is controlled by the body’s nervous system, akin to breathing and heartbeat, has led scientists to consider the evolutionary reasoning behind our wrinkled digits.

The investigation follows a paper by American scientist Mark Changizi, in the journal Brain Behaviour and Evolution, which suggested that wrinkles on fingers form a pattern that channels water away from the fingertip, much like rain water on tyre treads.

Dr. Smulders, from Newcastle’s Centre for Behaviour and Evolution, said the new findings open further avenues for research.

“This raises the question of why we don’t have permanently wrinkled fingers and we’d like to examine this further. Our initial thoughts are that this could diminish the sensitivity in our fingertips or could increase the risk of damage through catching objects.”

It also remains to be seen whether this phenomenon occurs in other animals.